They could also ensure that foods in cafeterias or vending machines follow food service guidelines.

If you are in the habit of having lunch from your workplace cafeteria, think twice. It tend to contain high amount of sodium and refined grains, calories and very little whole grains and fruit, leading to unhealthy eating putting you at risk of various disease including cancer, researchers warn.

The study over 5,000 employees from a US firm, showed that nearly a quarter had food from work at least once a week and that the average weekly calories obtained was almost 1,300.

The food tended to be high in empty calories -- those from solid fats and/or added sugars -- with more than 70 per cent of the calories coming from food that was obtained for free.

"Our results suggest that the foods people get from work do not align well with the recommendations in the dietary guidelines," said Stephen Onufrak, epidemiologist at the US Centers for Disease Control and Prevention.

"Since we found that a lot of the foods obtained by employees were free, employers may also want to consider healthy meeting policies to encourage healthy food options at meetings and social events," he suggested.

Workplaces can play more of a role to help ensure access to and promote healthier food options, the researchers said.

They suggest that employers could help their employees eat better at work by using worksite wellness programs to promote healthy options that are also appealing.

They could also ensure that foods in cafeterias or vending machines follow food service guidelines.

"Worksite wellness programmes have the potential to reach millions of working people and have been shown to be effective at changing health behaviours among employees, reducing employee absenteeism and reducing health care costs," Onufrak said.

The study, presented at the Nutrition 2018 meeting held in Boston, included data from 5,222 employees.